Soft, rigid, and hybrid bimodulus contact lenses have been manufactured and distributed in an effort to correct the naturally occurring refractive errors of the eye and the irregular refractive errors resulting from eye diseases like keratoconus and pellucid marginal degeneration, and from corneal surgery and ocular trauma.
Heretofore, soft contact lenses have been limited in their ability to correct irregular refractive errors due to the soft lens material deforming and taking the irregular shape of the underlying eye.
Rigid contact lenses have been limited in their use due to the complexity of fitting the lenses, the difficulty in reducing or eliminating the pressure of the rigid lens material on the underlying eye, and the problems relating to stagnation of the post lens tear environment.
Hybrid bimodulus contact lenses comprised of a rigid gas permeable material surrounded by a soft flexible material have solved some of the problems associated with rigid and soft contact lenses. However, lens flexure and the need to fit the lenses with a curvature that is substantially shorter in radius of curvature than the underlying eye are challenges to hybrid lens success. Further, in some cases the soft peripheral skirt of hybrid lenses fails to elevate the rigid central zone above the cornea and the resultant bearing of the rigid gas permeable material on the cornea is reported to cause discomfort and lens intolerance.
In view of the foregoing, there is an expressed need to provide lens optics with lenses that extend beyond the diameter of the cornea that do not demonstrate excessive pressure on the sclera and that allow for post lens tear exchange. There is also a need for a design and system of fitting scleral lenses that is easily understood so that the fitter can succeed in the determination of the successful lens parameters with minimal time and equipment, along with a reduced number of lens reorders, and achieve successful wearing by the patient.
Moreover, because of the uncurving nature of the sclera near the limbus, often neither a concave downward curve nor an uncurved landing zone can contact the sclera at just inside the lens edge to accomplish appropriate edge lift without impinging on the more peripheral sclera to the point of penetration. In response, such landing zone curves may cause the entire lens to be supported further above the cornea and contact the sclera with a very narrow support zone.
The present invention addresses these needs and other limitations of the prior art.